As modern electronic devices have continued to evolve, size reduction has become a preeminent design consideration. Indeed, shrinking device profiles have made pocket electronics possible while preserving robust processing capability. Much progress has been made in shrinking electronic components like integrated circuits. However, mechanical support systems have sometimes lagged behind electronic advances. At least one reason for this lag is that many mechanical structures are limited by strength to weight considerations. Thus, while a miniaturized circuit may consume ever shrinking profiles, a mechanical structure may be limited to a minimum size in order to achieve structural stability. In some examples, structural stability may include unwanted inefficiencies.
For example, FIG. 1 is an illustrative cross-sectional representation of a scrolling device portion 100. Embodiments of this device are described in detail in U.S. patent application Ser. No. 10/188,182 entitled, “TOUCH PAD HANDHELD DEVICE,” and in U.S. patent application Ser. No. 10/643,256 entitled, “MOVABLE TOUCH PAD WITH ADDED FUNCTIONALITY,” which are hereby incorporated by reference. Scrolling device portion 100 includes a cover 104 that provides a protection for the device. An adhesive layer 108 mechanically couples cover 104 with printed circuit board (PCB) 112. PCB 112 may provide structural support for electronic components like, for example, a capacitive sensor (not shown), an integrated circuit 128, a switch 120 and a connection pad 116. PCB's 112 structural rigidity provides at least some durability to the device, but its use is not without some inherent disadvantages.
For example, PCB's may be limited to a minimum thickness. Minimum thickness is due to structural requirements that may, in some examples, be unavoidable. Further, because a PCB is rigid, applications may, in some examples, require that features like integrated circuit 128, switch 120, and connection pad 116 be co-located with the PCB. Co-location requirements may add to the device stack height further limiting size reductions. Still further, co-location of associated electronic components, like a switch, for example, may ultimately lead to device failure due to cracked soldering or components as a result of stresses imparted on the PCB during switch cycling. Still further, PCB rigidity may result in some loss of tactile responsiveness of an electronic component like a switch, for example. Therefore scrolling input arrangements using capacitive sensors on a flexible membrane are presented herein.
As may also be appreciated, capacitive sensors such as those described above generally may respond undesirably in rapidly changing temperature conditions. For example, in a rapidly heating environment, both the environment as well as an input pointer such as a finger may cause an increase in capacitance signals on sensors. In current designs, if recalibration is conducted while a finger is present, the unit may “calibrate out” the finger. Thus, either the unit remains with an incorrect calibration or it does not respond to the finger. Thus, methods of calibrating a plurality of capacitive sensors in response to rapidly changing positive temperature gradients are presented herein.